Field of the Invention
The present invention relates to a technology of a sheet determination that determines a sheet type and a surface condition of a sheet, which is used suitably for a printing apparatus.
Description of the Related Art
Japanese Patent Laid-Open No. 2005-186357 discloses a method for determining the type of a sheet, which is used for printing, by using an optical sensor. The type of the sheet is determined by comparing an output value of the sensor with a threshold.
However, when performance of the optical sensor is degraded with the sensor having been used for a long period of time, there is a possibility that the determination of the sheet type by the set threshold is made in error. For example, in a printing apparatus of an inkjet system, ink mists float with a performance of printing and attach to optical components of the sensor (light-emitting elements, light-receiving elements or lens) to cause a light-receiving amount to be gradually smaller than the original amount.